Coupler assembly for coupling surgical instruments to robotic systems

ABSTRACT

A coupler assembly for selective connection of a surgical instrument to a robotic arm is provided. The coupler assembly includes a stationary hub and a rotation hub. The stationary hub has a first mating feature and is secured to a first one of the surgical instrument and the robotic arm. The rotation hub includes a support member and rotation member mounted on the support member. The support member is secured to a second one of the surgical instrument and the robotic arm. The rotation member is rotatable relative to the support member between a first state and a second state. The rotation member has a second mating feature that releasably couples to the first mating feature of the stationary hub as the rotation member rotates relative to the stationary hub.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/082,007, filed Sep. 4, 2018, which is a U.S. National StageApplication filed under 35 U.S.C. § 371(a) of International PatentApplication Serial No. PCT/US2017/020401, filed Mar. 2, 2017, whichclaims the benefit of U.S. Provisional Patent Application No.62/303,613, filed Mar. 4, 2016, the entire contents of each of which arehereby incorporated by reference herein.

BACKGROUND

Robotic surgical systems were widespread in minimally invasive medicalprocedures. As with surgical procedures performed manually by a surgeon,robotic surgical systems required the use of various surgicalinstruments in order to successfully complete the procedure. Thesesurgical instruments were operatively connected to a robotic arm andincluded several connecting features that enabled the surgeon to controlthe surgical instrument in a precise manner. These connections involvedthe complex interconnection of mechanical, electrical, and/or pneumaticfeatures. The particular procedure being performed often involvedfrequent installation and/or removal of one or more surgicalinstruments. Thus, in certain instances, instrument exchange wascumbersome and time consuming.

Accordingly, there is a need for new coupling devices and methods thatenable easy, quick, and reliable removal and/or installation of surgicalinstruments to robotic surgical systems.

SUMMARY

The present disclosure describes robotic devices, systems, and methodsthat demonstrate a practical approach to meeting the performancerequirements and overcoming the usability challenges associated withsurgical instrument exchange. In general, the present disclosuredescribes robotic surgical systems that include surgical instruments forconnection to robotic arms via coupler assemblies. The presentlydescribed coupler assemblies provide removal and/or installation of thesurgical instruments to the robotic arms with stationary and rotationhubs that removably couple to one another. The stationary hub is securedto the robotic arm or to the surgical instrument (or component thereof)while the rotation hub, which includes a rotation member and a supportmember, is secured to the other of the robotic arm of the surgicalinstrument (or component thereof). Rotation member of rotation hub andstationary hub each include complementary mating features that areselectively engageable with one another. The coupling and/or decouplingof stationary and rotation hubs can be effectuated by merely rotatingrotation member of rotation hub relative to support member of rotationhub to engage and/or disengage the complementary mating features. As thecomplementary mating feature engage and/or disengage, the surgicalinstrument can be easily, quickly, and reliably installed and/or removedto/from the robotic arm.

According to one aspect, a coupler assembly for selective connection ofa surgical instrument to a robotic arm is provided. In another aspect, arobotic surgical system including a surgical instrument, robotic arm,and a coupler assembly is provided.

The coupler assembly includes a stationary hub and a rotation hub. Thestationary hub has a first mating feature and is secured to a first oneof the surgical instrument and the robotic arm. The rotation hubincludes a support member and rotation member mounted on the supportmember. The support member is secured to a second one of the surgicalinstrument and the robotic arm. The rotation member is rotatablerelative to the support member between a first state and a second state.The rotation member has a second mating feature that releasably couplesto the first mating of the stationary hub as the rotation member rotatesrelative to the stationary hub.

In embodiments, the first mating feature of the stationary hub includesa boss and the second mating feature of the rotation hub includes a slotdefined in the rotation member. The boss is receivable within the slotto couple the stationary hub to the rotation hub. The rotation membermay include an outer surface that extends between top and bottomsurfaces. The slot may extend diagonally around the outer surface of therotation member and open through the bottom surface of the rotationmember. The rotation member may include a ledge that extends into theslot. The ledge is positioned to engage the boss while the rotationmember is in the first state. The boss is separable from the ledge asthe rotation member moves toward the second state.

The coupler assembly may further include a bias washer interposedbetween the rotation member and the support member of the rotation hub.The rotation member may include an inner surface having an inner flangeextending radially inwardly from the inner surface. The support membermay have an outer surface and an outer flange extending radiallyoutwardly from the outer surface of the support member. The bias washermay be supported on the inner flange of the rotation member and incontact with the outer flange of the support member. In certainembodiments, the bias washer includes a Bellville washer, a curved diskspring, a wave washer, or combinations thereof.

In embodiments, the rotation member includes a prong extending therefromand the support member includes an outer flange extending radiallyoutwardly from an outer surface of the support member. The outer flangemay define a second slot positioned to receive the prong of the rotationmember. The second slot may be arcuate.

In certain embodiments, the rotation member includes at least one secondprong. Each prong defines a groove therein such that the second prongand the grooves formed therein are positioned to receive a retentionring therein that inhibits axial movement of the rotation memberrelative to the support member.

The coupler assembly may further include a biasing element positionedwithin the second slot of the outer flange and in contact with theprong. The biasing element may be configured to compress as the prongtranslates through the second slot while the rotation member rotatesrelative to the support member. The biasing element biases the rotationelement toward the first state.

Further details and aspects of exemplary embodiments of the presentdisclosure are described in more detail below with reference to theappended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a schematic illustration of a robotic surgical system inaccordance with the present disclosure;

FIG. 2A is a perspective view of a robotic arm of the robotic surgicalsystem of FIG. 1 with a surgical instrument of the robotic surgicalsystem shown mounted to the robotic arm;

FIG. 2B is a perspective view illustrating the surgical instrument ofFIG. 2A shown separated from the robotic arm of FIG. 2A;

FIG. 3 is a perspective view, with parts separated, of a couplerassembly of the robotic surgical system of FIG. 1;

FIG. 4A is a side, perspective view of a stationary hub of the couplerassembly of FIG. 3;

FIG. 4B is a top view of the stationary hub of FIG. 4A;

FIG. 5 is a perspective view, with parts separated, of a rotation hub ofthe coupling assembly of FIG. 3;

FIG. 6A is a side view of a rotation member of the rotation hub of FIG.5;

FIG. 6B is a perspective view of the rotation member of FIG. 6A;

FIG. 7A is a side, perspective view of a support member of the rotationhub of FIG. 5; and

FIG. 7B is a top view of the support member of FIG. 7A.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described in detail below withreference to the drawings in which like reference numerals designateidentical or corresponding elements in each of the several views. Asused herein, the term “clinician” refers to a doctor, a nurse or anyother care provider and may include support personnel. Throughout thisdescription, the term “proximal” will refer to the portion of the deviceor component thereof that is closer to the clinician and the term“distal” will refer to the portion of the device or component thereofthat is farther from the clinician. Additionally, in the drawings and inthe description that follows, terms such as front, rear, upper, lower,top, bottom, and similar directional terms are used simply forconvenience of description and are not intended to limit the disclosure.In the following description, well-known functions or constructions arenot described in detail to avoid obscuring the present disclosure inunnecessary detail.

With reference to FIG. 1, a robotic surgical system in accordance withthe present disclosure is generally identified as reference numeral 1.Robotic surgical system 1 includes a plurality of robotic arms 2, 3, acontroller or control device 4, and an operating console 5 operablycoupled with control device 4. Operating console 5 includes a displaydevice 6, which is set up in particular to display three-dimensionalimages, and manual input devices 7 and 8, by means of which a clinician(not shown), for example, a surgeon, is able to telemanipulate roboticarms 2, 3. Each of the plurality of robotic arms 2, 3 includes aplurality of segments 3 x, each of which are connected through joints 3y to enable relative movement between the segments 3 x and/or joints 3y.

Referring also to FIGS. 2A and 2B, robotic surgical system 1 includes asurgical instrument 100 that releasably couples to a mount or mountingmember 3 a of robotic arms 2, 3 via a coupler assembly 200, as will bediscussed in further detail below. Surgical instrument 100 includes aninstrument drive unit 300 and a surgical instrument 400 that define alongitudinal axis “A” extending therethrough. In some embodiments,instrument drive unit 300 is fixedly secured to surgical instrument 400.In certain embodiments, surgical instrument 400 is detachably coupled toinstrument drive unit 300. Surgical instrument 400 includes an endeffector 430 disposed at a distal end thereof that is operativelycoupled to instrument drive unit 300 by one or more connector members“CM” (e.g., cables, rod, belts, chains, etc., or combinations thereof)to enable end effector 430 to perform one or more functions.

With reference to FIG. 1, robotic arms 2, 3 may be driven by electricdrives (not shown) that are connected to control device 4. Controldevice 4 (e.g., a computer) is set up to activate the drives such thatsurgical instrument 400 (including end effector 430), robotic arms 2, 3,and instrument drive units 300 (FIG. 2A) cooperate to execute a desiredmovement according to a movement defined by operation of manual inputdevices 7, 8. It is contemplated that control device 4 may activate thedrives by means of a computer program. Control device 4 may also be setup in such a way that it regulates movement of robotic arms 2, 3 and/orof the drives.

Robotic surgical system 1 is configured for use on a patient “P” lyingon a surgical table 12 to be treated in a minimally invasive manner bysurgical instruments such as surgical instrument 400. Robotic surgicalsystem 1 may also include more than two robotic arms 2, 3. Theadditional robotic arms are likewise connected to control device 4 andare telemanipulatable by operating console 5. One or more additionalsurgical instruments 100 and/or surgical instruments 400 may be attachedto any additional robotic arms 2, 3.

Control device 4 may control a plurality of motors (Motor 1 . . . n)with each motor configured to drive a pushing and/or a pulling of one ormore of connector members “CM” (see FIG. 2A) coupled to end effector 430of surgical instrument 400. In use, as connector members “CM” are pushedand/or pulled, connector members “CM” effect operation and/or movementof end effector 430 of surgical instrument 400. It is contemplated thatcontrol device 4 coordinates activation of the various motors (Motor 1 .. . n) to coordinate a pushing and/or a pulling motion of one or more ofconnector members “CM” in order to coordinate an operation and/ormovement of one or more end effectors 430 of robotic surgical system 1.

Control device 4 can include any suitable logic control circuit adaptedto perform calculations and/or operate according to a set ofinstructions. Control device 4 can be configured to communicate with aremote system “RS,” either via a wireless (e.g., Wi-Fi™, Bluetooth®,LTE™, etc.) and/or wired connection. Remote system “RS” can includedata, instructions and/or information related to the various components,algorithms, and/or operations of robotic surgical system 1. Remotesystem “RS” can include any suitable electronic service, database,platform, cloud “C,” or the like. Control device 4 may include a centralprocessing unit operably connected to memory. The memory may includetransitory type memory (e.g., RAM) and/or non-transitory type memory(e.g., flash media, disk media, etc.). In some embodiments, the memoryis part of, and/or operably coupled to, remote system “RS.”

Control device 4 can include a plurality of inputs and outputs forinterfacing with the components of robotic surgical system 1, such asthrough a driver circuit. Control device 4 can be configured to receiveinput signals and/or generate output signals to control one or more ofthe various components (e.g., one or more motors) of robotic surgicalsystem 1. The output signals can include, and/or can be based upon,algorithmic instructions which may be pre-programmed and/or input by auser. Control device 4 can be configured to accept a plurality of userinputs from a user interface (e.g., switches, buttons, touch screen,etc. of operating console 5) which may be coupled to remote system “RS.”

A database 14 can be directly and/or indirectly coupled to controldevice 4. Database 14 can be configured to store pre-operative data fromliving being(s) and/or anatomical atlas(es). Database 14 can includememory which can be part of, and/or or operatively coupled to, remotesystem “RS.” Reference may be made to U.S. Patent Publication No.2012/0116416, filed on Nov. 3, 2011, entitled “Medical Workstation,” theentire content of which is incorporated herein by reference, for adetailed discussion of the construction and operation of roboticsurgical system 1. Reference may also be made to InternationalApplication No. PCT/US2014/61329, filed on Oct. 20, 2014, entitled“Wrist and Jaw Assemblies for Robotic Surgical Systems,” the entirecontent of which is incorporated herein by reference, for a detaileddescription of the construction and/or operation of various componentsof a robotic surgical system.

Referring to FIGS. 2A, 2B, and 3, coupler assembly 200 generallyincludes a first or stationary hub 210 a, and a second or rotation hub210 b that releasably couples to stationary hub 210 a. It iscontemplated that coupler assembly 200, and/or components thereof, maybe formed from any suitable material capable of being used in a surgicalenvironment such as stainless steel, cobalt chrome, ceramics, polymers,or the like. Using any suitable fastening techniques such as frictionfit, welding, adhesives, and/or the like, coupler assembly 200, and/orcomponents thereof, can be secured to mount 3 a of robotic arm 3 and/orto surgical instrument 100. For example, stationary hub 210 a can besecured to mount 3 a while rotation hub 210 b is secured to surgicalinstrument 100, or vice versa, such that surgical instrument 100 can beselectively coupled and/or uncoupled to robotic arm 3.

Referring to FIGS. 4A and 4B, stationary hub 210 a of coupler assembly200 may have any suitable configuration such as cylindrical, square,rectangular, hexagonal, or the like. Stationary hub 210 a includes anouter surface 212 a and an inner surface 212 b. Outer surface 212 aincludes mating features 214 such as lugs or bosses that extend radiallyoutward therefrom and inner surface 212 b defines a throughbore 216 thatextends axially through stationary hub 210. Mating features 214 may beformed uniformly with stationary hub 210 a (e.g., a machined feature).In embodiments, mating features 214 may be separate bodies securedwithin respective counterbores or throughbores (not shown) definedwithin outer surface 212 a using any suitable fastening techniques suchas fastening, friction fit, welding, adhesives, and/or the like.Although generally shown as including three mating features 214 disposedthereon, it is contemplated that stationary hub 210 a may include anysuitable number of mating features 214. Mating features 214 are disposedin spaced relation to one another to enable rotation hub 210 b (FIG. 5)to selectively couple thereto, as will be described in further detailbelow. Mating features 214 may be placed at predetermined locationsabout outer surface 212 a of stationary hub 210 a. For example, as seenin FIG. 4B, mating features 214 may be disposed at equidistant radiallocations such as every 120 degrees or every 90 degrees in the case ofthree and four mating features 214, respectively.

With reference to FIG. 5, rotation hub 210 b includes a support member220, a rotation member 230, biasing elements 240, a bias washer 250, anda retention ring 260. The components of rotation hub 210 b are stackedalong a longitudinal axis “B.” Biasing elements 240 may include a coilspring or the like. Bias washer 250 may be any suitable biasing washersuch as a Bellville washer, curved disk spring, wave washer, or thelike. Retention ring 260 may include any suitable retention ring such asa washer, circlip, spiral retention ring, or the like.

As illustrated in FIGS. 6A and 6B, rotation member 230 of rotation hub210 b may have a body 232 with any suitable configuration such ascylindrical, square, rectangular, hexagonal, or the like. Body 232includes an outer surface 232 a, an inner surface 232 b, a lower surface232 c, and an upper surface 232 d. Inner surface 232 b defines a passage232 e therethrough and includes an inner flange 234 extending radiallyoutward from the inner surface 232 b to support bias washer 250.

Prongs 236 extend from upper surface 232 c of body 232, with each prong236 defining to a tooth 236 a. Although rotation member 230 is shownwith three prongs 236, it is contemplated that any suitable number ofprongs 236 may be disposed on upper surface 232 c of rotation member230. Prongs 236 may be arranged on upper surface 232 c of rotationmember 230 at predetermined locations therealong. For example, adjacentprongs 236 may be disposed 120 degrees apart. In some embodiments,spacing of prongs 236 may be dependent upon the number of prongs 236disposed on upper surface 232 c (e.g., 180 degrees for two prongs 236,90 degrees for three prongs 236, etc.). A groove 236 c is defined in aninner surface 236 b of each prong 236 that functions to releasablyretain retention ring 260 while retention and rotation members 220, 230are joined together to inhibit separation of retention and rotationmembers 220, 230. Collectively, grooves 236 c of prongs 236 define anannular channel 236 d within which retention ring 260 is supported.

Prongs 236 may have a resilient configuration that enables supportmember 220 to support retention ring 260 while retention and rotationmembers 220, 230 are coupled together. For example, prongs 236 may bedeflected outwardly from an initial condition to enable retention ring260 to be received within annular grooves 236 c of prongs 236. Prongs236 are biased to return to the initial condition to maintain retentionring 260 within grooves 236 c of prongs 236.

Mating features 238 such as diagonal slots are defined through inner andouter surfaces 232 a, 232 b of rotation member 230 at predeterminedlocations around body 232 of rotation member 230. Each mating feature238 extends vertically from lower surface 232 c of rotation member 230and is further defined by a protrusion or ledge 239 that extends intomating feature 238. Ledge 239 has a retaining surface 239 a that isparallel with upper surface 232 d of body 232 and an angled side surface239 b that intersects retaining surface 239 a. Mating features 238 arepositioned on body 232 of rotation member 230 to slidingly receivecorresponding bosses 214 (see FIGS. 4A and 4B) of stationary hub 210 aas rotation member 230 of rotating hub 210 b is rotated relative tostationary hub 210 a in a bayonet-type fashion.

With reference to FIGS. 7A and 7B, support member 220 of rotation hub210 b has a generally cylindrical configuration, although other suitableconfigurations are contemplated, such as square, rectangular, octagonal,and/or the like. In general, the configuration of support member 220 iscomplementary to that of bore 232 e of rotation member 230 (see FIGS. 6Aand 6B) such that support member 220 may be received within bore 232 eof rotation member 230.

Support member 220 includes an outer surface 222 a and an inner surface222 b. Inner surface 222 b defines a lumen 224 that extends axiallythrough support member 220. A flange 226 extends radially outwardly fromouter surface 222 a of support member 220 and may separate a length ofsupport member 220 between an upper portion 222 c and a lower portion222 d. Flange 226 may bisect upper and lower portions 222 c, 222 d andfunctions as a bearing surface that supports bias washer 250 whensupport member 220 is advanced within bore 232 e of rotation member 230such that bias washer 250 nests between inner flange 234 of rotationmember 230 and flange 226 of support member 220 (see FIG. 5).

Flange 226 defines slots 226 a therethrough that receive prongs 236 ofrotation member 230 and support biasing elements 240 therein. Slots 226a may have a generally arcuate shape with a radius proportional to aradius of flange 226. Slots 226 a are arranged at predeterminedlocations about flange 226. For example, slots 226 a may be disposed atequidistant locations such as every 120 degrees, however, slots 226 aare generally arranged in a complimentary configuration to that ofprongs 236 of rotation member 230 (see FIGS. 6A and 6B). Slots 226 a arepositioned to enable prongs 236 to slidably translate through slots 226a as rotation member 230 is rotated relative to support member 220and/or stationary hub 210 a, as described in further detail below.

In operation, to attach surgical system 100 to one of robotic arms 2, 3,a clinician positions stationary and/or rotation hub 210 a, 210 b suchthat mating features 214 of stationary hub 210 a are aligned with matingfeatures 238 of rotation member 230. Stationary and rotation hubs 210 a,210 b are then approximated until bosses 212 of stationary hub 210 a arepositioned within mating features 238 and secured against retainingsurface 239 a. As indicated by arrow “R” shown in FIG. 3, relativerotation between stationary and rotation hub 210 a, 210 b may facilitatereception of mating features 214 of stationary hub 210 a within matingfeatures 238 of rotation hub 210 b. To facilitate reception of matingfeatures 214 of stationary hub 210 a within mating features 238 ofrotation hub 210 b, relative rotation between stationary and rotationhub 210 a, 210 b may involve rotating mount 3 a of robotic arm 3relative to surgical instrument 100 (or components thereof) and/orrotating surgical instrument 100 (or components thereof) relative tomount 3 a. Additionally and/or alternatively, rotation member 230 ofrotation hub 210 b may be rotated relative to support member 220 tofacilitate reception of mating features 214 of stationary hub 210 awithin mating features 238 of rotation hub 210 b.

With rotation member 230 biased to an initial, unrotated state underspring force (a rotational biasing force), exerted by biasing members240 against prongs 236, rotation of rotation member 230, as indicated byarrows “R” of FIG. 3, slides prongs 236 of rotation member 230 throughslots 226 a of support member 220 towards biasing elements 240,compressing biasing elements 240 from an extended state to a compressedstate. Upon release of applied rotational forces acting on rotationmember 230, to effectuate rotation thereof, the spring force of biasingelements 240, which is counter to the applied rotational forces, causesrotation member 230 to return to its initial, unrotated state.

Once stationary and/or rotation hub 210 a, 210 b are coupled togetherwith rotation member 230 of rotation hub 210 b disposed in its initial,unrotated state, mating features 214 of stationary hub 210 a are securedagainst ledge 239 of rotation hub 210 b under the spring force impartedby biasing members 240 of rotation hub 210 b against prongs 236 ofrotation hub 210 b. Also while stationary and/or rotation hub 210 a, 210b are coupled together in this position, bias washer 250 provides anaxial biasing force against mating features 214 of stationary hub 210 ato inhibit axial movement of rotation member 230 of rotation hub 210 bwith respect to stationary hub 210 a along axis “A.”

When an instrument exchange or removal is desired, rotation member 230of rotation hub 210 b can be rotated against the rotational biasingforce of biasing elements 240 so as to compress biasing elements 240 asprongs 236 of rotation member 230 rotate along slots 226 a of supportmember 220 as described above. As rotation member 230 is rotated, matingfeatures 214 of stationary hub 210 a separate from mating features 238of rotation hub 210 b, enabling stationary and rotation hubs 210 a, 210b to separate for freeing surgical instrument 100 (and/or componentsthereof) from robotic arm 3. Surgical instrument 100 (and/or componentsthereof) can then be reinserted or replaced with a different surgicalinstrument 100 (and/or component thereof) similar to that describedabove as desired. For example, a different surgical instrument 100 mayinclude a different end effector that functions differently than endeffector 430 of surgical instrument 100 (e.g., an instrument that sealsversus an instrument that fastens) to effectuate a different aspect ofthe surgical procedure.

In some embodiments, mating features 214, 238 of stationary and rotationhubs 210 a, 210 b are reversed such that stationary hub 210 a definesmating features 238 and rotation hub 210 b includes mating features 214.In certain embodiments, both of stationary and rotation hubs 210 a, 210b include one or more mating features 214 and one or more matingfeatures 238 such that corresponding mating features of stationary androtation hubs 210 a, 210 b are positioned to align with its respectcomplementary mating feature on the other of the stationary and rotationhub 210 a, 210 b.

Persons skilled in the art will understand that the structures andmethods specifically described herein and shown in the accompanyingfigures are non-limiting exemplary embodiments, and that thedescription, disclosure, and figures should be construed merely asexemplary of particular embodiments. It is to be understood, therefore,that the present disclosure is not limited to the precise embodimentsdescribed, and that various other changes and modifications may beeffected by one skilled in the art without departing from the scope orspirit of the disclosure. Additionally, the elements and features shownor described in connection with certain embodiments may be combined withthe elements and features of certain other embodiments without departingfrom the scope of the present disclosure, and that such modificationsand variations are also included within the scope of the presentdisclosure. Accordingly, the subject matter of the present disclosure isnot limited by what has been particularly shown and described.

What is claimed:
 1. A coupler assembly for selective connection of asurgical instrument to a robotic arm, the coupler assembly comprising: astationary hub having a first mating feature, the stationary hub securedto a first one of the surgical instrument and the robotic arm; and arotation hub including a support member and rotation member mounted onthe support member, the support member secured to a second one of thesurgical instrument and the robotic arm, the rotation member rotatablerelative to the support member between a first state and a second state,the rotation member having a second mating feature that releasablycouples to the first mating feature of the stationary hub as therotation member rotates relative to the stationary hub.
 2. The couplerassembly of claim 1, wherein the first mating feature of the stationaryhub includes a boss and the second mating feature of the rotation hubincludes a slot defined in the rotation member, the boss beingreceivable within the slot to couple the stationary hub to the rotationhub.
 3. The coupler assembly of claim 2, wherein the rotation memberincludes an outer surface that extends between top and bottom surfaces,the slot extending diagonally around the outer surface of the rotationmember and opening through the bottom surface of the rotation member. 4.The coupler assembly of claim 2, wherein the rotation member includes aledge that extends into the slot, the ledge positioned to engage theboss while the rotation member is in the first state, the boss beingseparable from the ledge as the rotation member moves toward the secondstate.
 5. The coupler assembly of claim 1, further including a biaswasher interposed between the rotation member and the support member ofthe rotation hub.
 6. The coupler assembly of claim 5, wherein therotation member includes an inner surface having an inner flangeextending radially inwardly from the inner surface, the support memberhaving an outer surface and an outer flange extending radially outwardlyfrom the outer surface of the support member, the bias washer supportedon the inner flange of the rotation member and in contact with the outerflange of the support member.
 7. The coupler assembly of claim 6,wherein the bias washer includes a Bellville washer, a curved diskspring, a wave washer, or combinations thereof.
 8. The coupler assemblyof claim 2, wherein the rotation member includes a prong extendingtherefrom and the support member includes an outer flange extendingradially outwardly from an outer surface of the support member, theouter flange defining a second slot positioned to receive the prong ofthe rotation member.
 9. The coupler assembly of claim 8, wherein thesecond slot is arcuate.
 10. The coupler assembly of claim 8, wherein therotation member includes at least one second prong, each prong defininga groove therein, wherein the second prong and the grooves formedtherein are positioned to receive a retention ring therein that inhibitsaxial movement of the rotation member relative to the support member.